U.S. patent number 6,428,747 [Application Number 09/430,219] was granted by the patent office on 2002-08-06 for integrated extracorporeal blood oxygenator, pump and heat exchanger system.
This patent grant is currently assigned to Cardiovention, Inc.. Invention is credited to Jean-Pierre Dueri, Robert Jochim, Alex Leynov.
United States Patent |
6,428,747 |
Dueri , et al. |
August 6, 2002 |
Integrated extracorporeal blood oxygenator, pump and heat exchanger
system
Abstract
An integrated blood pump, oxygenator and heat exchanger is
provided having a rotating hollow fiber bundle assembly. A
plurality of vanes arranged along a central shaft of the device
increase pressure near the center of the fiber bundle to develop
sufficient pressure head to pump the blood through the heat
exchanger. In alternative embodiments, the heat exchanger comprises
a pleated metal wall, a bundle of non-permeable hollow fibers, or a
coiled tub disposed between the rotating hollow fiber bundle and an
interior wall of the housing.
Inventors: |
Dueri; Jean-Pierre (Sunnyvale,
CA), Jochim; Robert (Dublin, CA), Leynov; Alex
(Walnut Creek, CA) |
Assignee: |
Cardiovention, Inc. (Santa
Clara, CA)
|
Family
ID: |
26918022 |
Appl.
No.: |
09/430,219 |
Filed: |
October 29, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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223676 |
Dec 30, 1998 |
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Current U.S.
Class: |
422/46; 422/48;
604/4.01; 604/6.13; 604/6.14 |
Current CPC
Class: |
A61M
1/1629 (20140204); A61M 1/1625 (20140204); A61M
1/267 (20140204); A61M 1/262 (20140204); F28F
21/062 (20130101); A61M 1/1698 (20130101); A61M
60/113 (20210101); A61M 60/40 (20210101); A61M
60/818 (20210101); A61M 60/205 (20210101); A61M
60/419 (20210101); A61M 2205/366 (20130101) |
Current International
Class: |
A61M
1/16 (20060101); A61M 1/10 (20060101); A61M
1/26 (20060101); A61M 037/00 (); A61M 001/14 ();
A61N 001/36 () |
Field of
Search: |
;422/44-48
;604/4.01,6.09,6.11,6.13,6.14
;96/4,7-11,243,267-69,303-305,355-360,361
;210/321.81,321.9,321.72,321.78,321.87,500.23,348,456,257,295,433.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bockelman; Mark
Assistant Examiner: Bianco; P M
Attorney, Agent or Firm: Fish & Neave Pisano; Nicola
A.
Parent Case Text
REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent
application Ser. No. 09/223,676, filed Dec. 30, 1998.
Claims
What is claimed is:
1. A system for processing blood comprising: a housing having an
interior wall, a gas inlet, a gas outlet, a blood inlet, a blood
outlet, a coolant inlet and a coolant outlet; a shaft disposed
within the housing; an annular bundle of hollow fibers disposed for
rotation on the shaft, the annular bundle having a first end in
fluid communication with the gas inlet, a second end in fluid
communication with the gas outlet, and a central void in fluid
communication with the blood inlet; a plurality of vanes disposed
within the central void and affixed to the shaft; and a heat
exchanger element having an exterior surface disposed within the
housing between the annular bundle and the interior wall of the
housing, an interior of the heat exchanger element in fluid
communication with the coolant inlet and the coolant outlet,
wherein rotation of the annular bundle causes blood received within
the central void to pass outward through the annular bundle, flow
around the exterior surface of the heat exchanger element, and exit
through the blood outlet.
2. The apparatus of claim 1 wherein the heat exchanger element
comprises a coiled tube that surrounds the annular bundle.
3. The apparatus of claim 2 wherein the coiled tube comprises a
plurality of adjacent turns spaced apart relative to one another to
form gaps.
4. The apparatus of claim 1 further comprising a first plurality of
vanes that accelerate blood prior to entry into the central
void.
5. The apparatus of claim 4 wherein the first plurality of vanes is
mounted on the shaft.
6. A method for processing blood comprising: providing apparatus
comprising a housing having a gas inlet and a gas outlet, a coolant
inlet and a coolant outlet, a blood inlet and a blood outlet, an
annular bundle of hollow fibers disposed on a shaft for rotation
within the first housing and having a first end in fluid
communication with the gas inlet, a second end in fluid
communication with the gas outlet, and a central void, a plurality
of vanes disposed within the central void and affixed to the shaft,
and a heat exchanger in fluid communication the coolant inlet and
the coolant outlet; causing blood to flow into the housing and the
central void; rotating the plurality of vanes; causing a gas
comprising oxygen to flow through the hollow fibers of the annular
bundle; rotating the annular bundle to oxygenate blood flowing
through the housing and to develop sufficient pressure head to
cause the oxygenated blood to flow through the heat exchanger; and
transferring heat to or from blood flowing through the heat
exchanger.
7. The method of claim 6 wherein the apparatus further comprises a
first plurality of vanes that accelerate blood prior to entry into
the central void, the method further comprising rotating the first
plurality of vanes.
8. The method of claim 7 wherein the first plurality of vanes is
mounted to the shaft and are rotated at an angular velocity
identical to an angular velocity of the annular bundle.
9. The method of claim 6 wherein heat exchanger comprises a coiled
tube disposed within the housing surrounding the annular bundle,
and transferring heat to or from blood flowing through the heat
exchanger comprises causing the blood to contact an exterior
surface of the coiled tube.
10. A method for processing blood comprising: providing apparatus
comprising a housing having a gas inlet and a gas outlet, a coolant
inlet and a coolant outlet, a blood inlet and a blood outlet, an
annular bundle of hollow fibers disposed on a shaft for rotation
within the first housing and having a first end in fluid
communication with the gas inlet, a second end in fluid
communication with the gas outlet, and a central void, a first
plurality of vanes that accelerate blood prior to entry into the
central void, and a heat exchanger in fluid communication the
coolant inlet and the coolant outlet; causing blood to flow into
the housing; rotating the first plurality of vanes; causing blood
to flow into the central void; causing a gas comprising oxygen to
flow through the hollow fibers of the annular bundle; rotating the
annular bundle to oxygenate blood flowing through the housing and
to develop sufficient pressure head to cause the oxygenated blood
to flow through the heat exchanger; and transferring heat to or
from blood flowing through the heat exchanger.
11. The method of claim 10, wherein the heat exchanger comprises a
coiled tube disposed within the housing surrounding the annular
bundle, and transferring heat to or from blood flowing through the
heat exchanger comprises causing the blood to contact an exterior
surface of the coiled tube.
12. The method of claim 10, wherein the apparatus further comprises
a plurality of vanes disposed within the central void and affixed
to the shaft, the method further comprising rotating the plurality
of vanes.
13. The method of claim 10, wherein the first plurality of vanes is
mounted to the shaft and are rotated at an angular velocity
identical to an angular velocity of the annular bundle.
Description
FIELD OF THE INVENTION
The present invention relates to integrated extracorporeal
oxygenation and pumping systems having an integrated heat
exchanger.
BACKGROUND OF THE INVENTION
Each year hundreds of thousands of people are afflicted with
vascular diseases, such as arteriosclerosis, that result in cardiac
ischemia. For more than thirty years, such disease, especially of
the coronary arteries, has been treated using open surgical
procedures, such as coronary artery bypass grafting. During such
bypass grafting procedures, a sternotomy is performed to gain
access to the pericardial sac, the patient is put on
cardiopulmonary bypass, and the heart is stopped using a
cardioplegia solution.
Recently, the development of minimally invasive techniques for
cardiac bypass grafting, for example, by Heartport, Inc., Redwood
City, Calif., and CardioThoracic Systems, Inc., Cupertino, Calif.,
have placed a premium on reducing the size of equipment employed in
the sterile field. Whereas open surgical techniques typically
provide a relatively large surgical site that the surgeon views
directly, minimally invasive techniques require the placement of
endoscopes, video monitors, and various positioning systems for the
instruments. These devices crowd the sterile field and can limit
the surgeon's ability to maneuver.
At the same time, however, the need to reduce priming volume of the
oxygenator and pump, and the desire to reduce blood contact with
non-native surfaces has increased interest in locating the
oxygenator and pump as near as possible to the patient.
In recognition of the foregoing issues, some previously known
cardiopulmonary systems have attempted to miniaturize and integrate
certain components of cardiopulmonary systems. U.S. Pat. Nos.
5,266,265 and 5,270,005, both to Raible, describe an extracorporeal
blood oxygenation system having an integrated blood reservoir, an
oxygenator formed from a static array of hollow fibers, a heat
exchanger, a pump and a pump motor that is controlled by cable
connected to a control console.
The systems described in the foregoing patents employ relatively
short flow paths that may lead to inadequate gas exchange, due to
the development of laminar flow zones adjacent to the hollow
fibers. U.S. Pat. No. 5,411,706 to Hubbard et al. describes one
solution providing a longer flow path by recirculating blood
through the fiber bundle at a higher flow rate than the rate at
which blood is delivered to the patient. U.S. Pat. No. 3,674,440 to
Kitrilakis and U.S. Pat. No. 3,841,837 to Kitrilakis et al.
describe oxygenators wherein the gas transfer surfaces form an
active element that stirs the blood to prevent the buildup of
boundary layers around the gas transfer surfaces.
Makarewicz et al., "New Design for a Pumping Artificial Lung,"
ASAIO Journal, 42(5):M615-M619 (1996), describes an integrated
pump/oxygenator having a hollow fiber bundle that is potted between
an inlet gas manifold and an outlet gas manifold. The fiber bundle
is rotated at high speed to provide pumping action, while oxygen
flowing through the fiber bundle oxygenates the blood. Like the
device described in Ratan et al., "Experimental evaluation of a
rotating membrane oxygenator," J. Thoracic & Cardio. Sura.,
53(4):519-526 (1967), a separate heat exchanger must be used for
cooling the blood.
U.S. Pat. No. 5,830,370 to Maloney et al. describes a device having
a fiber bundle mounted for rotation between a fixed central
diffuser element and an outer wall of a housing. The fiber bundle
is rotated at speeds sufficiently high to cause shear forces that
induce turbulent flow within the blood. Rotation of the fiber
bundle is also used to augment heat exchange between the blood and
a coolant surrounding a portion of the blood reservoir. The limited
heat transfer surface area provided in such designs, however, may
be insufficient to provide adequate cooling.
Other patents for systems having stationary fiber bundles also have
addressed the role of the heat exchanger in an integrated assembly.
For example, U.S. Pat. No. 3,768,977 to Brumfield et al. describes
a blood oxygenator in which gas exchange and temperature regulation
occur in the same chamber to reduce the risk of gas bubble
evolution and gas embolism stemming from elevated blood
temperatures. U.S. Pat. No. 4,791,054 to Hamada et al. describes an
integrated heat exchanger and blood oxygenator that uses hollow
fibers, formed of an organic material, as the heat transfer tubes.
U.S. Pat. No. 5,770,149 to Raible et al. describes an integrated
blood pump, heat exchanger, and membrane oxygenator in which heat
exchange occurs after pumping but before oxygenation.
Although the devices having rotating fiber bundles described in the
foregoing references offer some desirable features, such as low
priming volume and low surface area, it is unclear whether such
devices can provide adequate heat exchange capability, due to
either limited heat transfer area or inadequate pump head to
provide flow through a separate heat exchanger over a wide range of
flow rates.
In view of the foregoing, it would be desirable to provide an
integrated extracorporeal blood oxygenator, pump and heat exchanger
having a rotating fiber bundle that provides compact size, low
priming volume, low surface area and adequate temperature
regulation.
It also would be desirable to provide an integrated extracorporeal
blood oxygenator, pump and heat exchanger with a hollow fiber
bundle having a rotating fiber bundle, and also providing adequate
heat transfer area between the blood and the coolant to facilitate
regulation of the blood temperature.
It further would be desirable to provide an integrated
extracorporeal blood oxygenator, pump and heat exchanger having a
rotating hollow fiber bundle that provides adequate pump head to
account for pressure head losses in the heat exchanger over a wide
range of blood flow rates.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention
to provide an integrated extracorporeal blood oxygenator, pump and
heat exchanger having a rotating fiber bundle that provides compact
size, low priming volume, low surface area and adequate temperature
regulation.
It is another object of the present invention to provide an
extracorporeal blood oxygenator, pump and heat exchanger with a
hollow fiber bundle having a rotating fiber bundle and also having
adequate heat transfer area between the blood and the coolant to
facilitate regulation of the blood temperature.
It is yet another object of this invention to provide an integrated
extracorporeal blood oxygenator, pump and heat exchanger having a
rotating hollow fiber bundle that provides adequate pump head to
account for pressure head losses in the heat exchanger over a wide
range of blood flow rates.
These and other objects of the invention are accomplished by
providing an integrated extracorporeal blood oxygenator, pump and
heat exchanger, suitable for use within a sterile field, that has a
low priming volume and low surface area. In accordance with the
principles of the present invention, the oxygenator, pump and heat
exchanger system includes a rotating hollow fiber bundle assembly
that both oxygenates the blood and develops sufficient pressure
head to pump the blood through an integral heat exchanger in fluid
communication with the blood flow path. In addition, heat exchanger
has a compact size but provides sufficient heat transfer area to
facilitate temperature regulation of blood flowing through the
device.
In one preferred embodiment, the heat exchanger comprises a metal
waffle-like wall disposed in a separate compartment of the housing,
so that blood passes along one side of the wall while coolant
passes along the opposite side of the wall. In an alternative
embodiment, the heat exchanger comprises a stationary bundle of
non-permeable hollow fibers through which blood flows, while a
coolant passes along the exterior of the bundle.
In yet another alternative embodiment, the heat exchanger comprises
a coiled metal tube disposed in a housing between the rotating
fiber bundle and the housing wall. Coolant passes through an
interior lumen of the coiled tube to absorb heat from (or
alternatively, transfer heat to) blood passing along the exterior
of the rotating fiber bundle.
Methods of using the integrated system of the present invention are
also provided.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features of the invention, its nature and various
advantages will be more apparent from the accompanying drawings and
the following detailed description of the preferred embodiments, in
which:
FIG. 1 is a perspective view of an integrated blood oxygenator and
pump system suitable for implementing the present invention;
FIGS. 2A and 2B are, respectively, side-sectional and cut-away
views of the device of FIG. 1;
FIG. 3 is a partial view of alternative embodiment of a central
shaft suitable for use in the device of FIG. 1;
FIG. 4 is a perspective view of an integrated oxygenator, pump and
heat exchanger constructed in accordance with the present
invention;
FIGS. 5A and 5B are, respectively, a cut-away view of a first
illustrative embodiment of a heat exchanger portion of the device
of FIG. 4, and a detailed side view of the pleated wall of the
device of FIG. 5A;
FIGS. 6A and 6B are, respectively, a side-sectional view and a
partial perspective view of an alternative embodiment of the heat
exchanger portion of the device of FIG. 4; and
FIGS. 7A-7C are, respectively, a partial perspective exterior view,
side-sectional view, and perspective cut-away view of an
alternative embodiment of the device of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides an integrated blood oxygenator,
pump, and heat exchanger system that combines active blood
oxygenation using a rotating fiber bundle with a large heat
transfer area and high pumping head, thereby overcoming the
drawbacks of previously known devices. In accordance with the
principles of the present invention, the device may be placed in or
near the sterile field and preferably has a low priming volume,
e.g., 200 cc or less.
Referring to FIGS. 1, 2A and 2C, an integrated blood
oxygenator/pump 10 suitable for implementing a device in accordance
with the principles of the present invention is described.
Pump/oxygenator 10 is of the type described in co-pending, commonly
assigned U.S. patent application Ser. No. 09/223,676, filed Dec.
30, 1998, which is incorporated herein by reference, and includes
several improvements over the previously known rotating fiber
bundle designs.
Pump/oxygenator 10 is magnetically coupled to drive shaft 11 of
motor 12, which is in turn controlled by controller 13.
Deoxygenated venous blood is supplied to pump/oxygenator 10 via
suitable biocompatible tubing (not shown) coupled to venous blood
inlet 14; oxygenated blood passes out of pump/oxygenator 10 through
blood outlet 15. Pressurized oxygen is introduced into
pump/oxygenator 10 via gas inlet port 16, while a mixture of oxygen
and carbon dioxide exits pump/oxygenator 10 via gas outlet port 17.
Alternatively, gas may be introduced into device 10 with a reversed
flow path, i.e., gas outlet port 17 is used as the gas inlet and
gas inlet port 16 is used as the gas outlet.
Motor 12, magnetically coupled drive shaft 11 and controller 13 are
items per se known in the art, and may comprise any of a number of
systems available from Bio-Medicus, Inc., Eden Prairie, Minnesota.
Alternatively, drive shaft 11, motor 12 and controller 13 may be
miniaturized to permit their placement closer to the patient.
Referring now to FIGS. 2A and 2B, pump/oxygenator 10 comprises
housing 20 enclosing fiber bundle assembly 21 that rotates within
housing 20 on shaft 22. Shaft 22 is affixed to shaft impeller 23,
which is attached to tray 24. Tray 24 holds one or more magnets 25
that are used to magnetically couple fiber bundle assembly 21 to
drive shaft 11.
Fiber bundle 26 preferably comprises a multiplicity of microporous
hollow fiber elements having an upper end potted in region 27, so
that the interior lumens of the fibers communicate with plenum 28
in inlet gas manifold 29. Likewise, the lower ends of the hollow
fiber elements of fiber bundle 26 are potted in region 30, so that
the interior lumens of the fibers communicate with plenum 31 in
outlet gas manifold 32. Any of a number of suitable biocompatible
potting materials may be used, such as polyurethanes or
epoxies.
Shaft 22 includes inner tube 33 and outer tube 34 arranged
coaxially to form annulus 35. Annulus 35 communicates with gas
inlet port 16 (see FIG. 1) via through-wall holes 37, and with
plenum 28 of inlet gas manifold 29 via through-wall holes 39 and
passageways 40 in plurality of pumping vanes 41. Lumen 42 of inner
tube 33 communicates with gas outlet port 17 at its upper end and
plenum 31 in outlet gas manifold 32 at its lower end via
passageways 44 in shaft impeller 23. Shaft seal 46a separates space
47, which couples gas outlet port 17 to lumen 42, from space 48,
which couples gas inlet port 16 (see FIG. 1) to annulus 35. Shaft
seal 46b separates space 48 from the interior of housing 20, which
encloses fiber bundle assembly 21.
Shaft 22 is carried in bearing 49, while shaft impeller 23 is
carried on bearings 51 and 52. Thrust washer 53 is interposed
between bearings 51 and 52, and the entire assembly is in turn
carried on bearing shaft 54. Bearing shaft 54 is affixed to lower
plate 55 of housing 20 by shoulder screw 56, and is seated on
O-ring seal 57. Shoulder screw 56 also is sealed with O-ring 58.
Shaft impeller 23 seals the lower end of annulus 35, while the
upper end of the annulus is sealed by plug 59.
Shaft impeller 23 (see FIG. 2B) has upper hub 60 and lower hub 61.
Upper hub 60 is connected to upper potting 27 and lower hub 61 is
connected to lower potting 30. Pumping vanes 62 extend between
annulus 23 and upper hub 60, and openings 63 between the plurality
of vanes 62 permit blood entering pump/oxygenator 10 via venous
blood inlet 14 to flow into void V of fiber bundle 26. Vanes 62 are
configured to serve as vanes that pump and accelerate blood passing
through the fiber bundle 26. Optionally, shaft impeller 23 may
include spiral vanes 65 between upper hub 60 and lower hub 61.
Baffle plate 66 is disposed in plenum 31, and includes grooves 67
on its underside that communicate with passageways 44. Baffle plate
66 thus causes gas exiting fiber bundle 26 to pass around the
outermost edge of the baffle plate. Accordingly, blood leaking into
plenum 31 of outlet gas manifold 32 is cleared from the manifold
and entrained in the exhaust gas stream passing through gas outlet
port 17.
FIG. 3 shows an alternative embodiment of shaft impeller 23, where
helical vanes 65 extend above hub 60 to further augment the pump
head developed by rotation of shaft impeller 23 and fiber bundle
26. As will of course be appreciated, the pump housing and seal
locations must be appropriately modified to accommodate extended
vanes 65 of FIG. 3.
As described in the above-incorporated application, the
construction of pump/oxygenator 30 includes a number of
advantageous features relative to previously-known rotating fiber
bundle systems, including reduced microbubble generation, reduced
shear-induced blood trauma, reduced flooding associated with fiber
breakage, and reduced stress-induced failure of fibers. Further
descriptions of those advantages may be found in the
above-incorporated application.
Referring now to FIG. 4, integrated apparatus 70 constructed in
accordance with the principles of the present invention is
described. Device 70 includes a pump/oxygenator component within
housing 71 that is similar in construction to pump/oxygenator 10 of
FIG. 1. Device 70 in addition includes an integrated heat exchanger
that overcomes drawbacks associated with heat exchangers used in
previously known rotating fiber bundle pump/oxygenators.
In particular, device 70 is magnetically coupled to drive shaft 72
of motor 73, which is in turn controlled by controller 74.
Pressurized oxygen is introduced into housing 71 via gas inlet port
75, while a mixture of oxygen and carbon dioxide exits housing 71
via gas outlet port 76. Deoxygenated venous blood is supplied to
device 70 through venous blood inlet 77; oxygenated blood passes
out of housing 71 and into heat exchanger 79. Heated, oxygenated
blood passes out of device 70 via blood outlet 80.
Heat exchange fluid, e.g. water, enters heat exchanger 79 at fluid
inlet 81 at a user-selected flow rate and heat content. The fluid
exchanges thermal energy with the oxygenated blood inside heat
exchanger 79 en route to fluid outlet 82. By varying the inlet
temperature and flow rate of the coolant, the oxygenated blood may
be regulated to a desired temperature before exiting heat exchanger
79 before the blood is returned to the patient via blood outlet 80.
As will be apparent to one skilled in the art of heat exchanger
design, temperature regulation alternatively may be achieved prior
to oxygenating the blood, or at multiple points along the blood
flow path.
Referring now to FIGS. 5A and 5B, an illustrative embodiment of
heat exchanger 79 of FIG. 4, is described. Heat exchanger 79
comprises pleated stainless steel wall 83 disposed in housing 84
using suitable biocompatible potting material to form blood side
compartment 85 and coolant side compartment 86. Additionally, as
illustrated in FIG. 5B, wall 83 may itself be corrugated to further
increase the heat transfer area. As will be appreciated by those
familiar with heat exchanger design, the pleating of wall 83
increases the overall area for heat transfer. As will further be
appreciated, coolant side 86 of heat exchanger may be used to
either transfer heat to, or absorb heat from, blood in contact with
the blood side of wall 83, depending upon the temperature of the
fluid introduced into coolant side compartment 86.
Heat exchanger fluid, e.g. water, flows into heat exchanger 79 via
fluid inlet 81, and travels through coolant side compartment 86
along a serpentine path to fluid outlet 82. This serpentine path
may be accomplished, for example, using ribs that extend inwardly
from wall 87 of coolant side compartment 86, to ensure that coolant
passing through coolant side compartment 86 contacts the coolant
side of pleated wall 83. Alternatively, such ribs may be omitted,
and stagnation zones within coolant side compartment 86 reduced by
passing the coolant through the compartment at a relatively high
flow rate.
Oxygenated blood enters blood side compartment 85 via a
through-wall opening between heat exchanger housing 84 and housing
71. Alternatively, blood outlet 15, as shown in FIG. 1, may be
provided in housing 70, and a separate piece of tubing used to
couple the blood outlet to a blood inlet (not shown) of heat
exchanger 79. The blood then travels through blood side compartment
85 to blood outlet 80.
Pleated wall 83 preferably is formed from a thin sheet of a highly
conductive material, e.g. stainless steel, that has been bent back
and forth upon itself to create a pleated structure with a large
surface area composed of small channels. The channels are
accessible on alternating sides of wall 83, so that blood in
contact with wall 83 in blood side compartment 85 flows through the
channels interdigitated with channels through which heat exchanger
fluid in coolant side compartment 86 flows, and vice versa. Over a
large surface area, the blood and heat exchanger fluid are only
separated by the highly conductive, thin metal sheet, thereby
enabling efficient thermal energy transfer.
With reference to FIGS. 6A and 6B, an alternative embodiment of a
heat exchanger element constructed in accordance with the present
invention is described. Heat exchanger 90 includes housing 91 which
may be coupled to or integrally formed with the housing 71. Housing
91 includes lower plenum 92, heat transfer region 93, upper plenum
94, and blood inlet 95. Bundle 96 of non-permeable hollow fibers
(only a few of which are depicted in FIG. 6A) is potted in tube
sheets 97 and 98 at either end of heat transfer region 93.
As indicated by the arrows in FIG. 6A, oxygenated blood enters
lower plenum 92 through inlet 95, passes through bundle 96 of
hollow fibers and exits into upper plenum 94, and is returned to
the patient via blood outlet 99. Heat transfer fluid, e.g. water,
flows through fluid inlet 81 into heat transfer region 93, where it
contacts the exterior surfaces of the fibers carrying oxygenated
blood. The heat transfer fluid exits heat transfer region 93 via
fluid outlet 82.
Advantageously, because heat exchanger 90 constitutes an integral
part of the overall device, the pressure drop imposed by heat
exchanger 90 may be readily accounted for in developing flow rate
versus bundle angular velocity characteristic curves. In this way,
the blood flow rate at the output of the heat transfer provided by
the device may be empirically determined as a function of the
bundle angular velocity. This information may in turn be used to
generate flow rate profiles for controller 74 (see FIG. 4) as a
function of bundle angular velocity.
Referring now to FIGS. 7A-7C, another alternative embodiment of an
integrated apparatus constructed in accordance with the principles
of the present invention is described. In FIG. 7A, a portion of
integrated device 110 is shown, from which the upper portion of
housing 113 has been omitted (compare to FIG. 2A). In this
embodiment, heat transfer fluid enters through fluid inlet 81 and
exits through fluid outlet 82 after passing through a coiled
tubing, described hereinbelow. Blood entering device 110 via the
venous inlet on the upper portion of housing 113 (not shown) exits
the device via blood outlet 15.
With respect to FIGS. 7B and 7C, integrated device 110 includes
annular fiber bundle 115 potted in regions 116 and 117 in manifolds
118 and 119, respectively. Manifolds 118 and 119 define inlet
plenum 120 and outlet plenum 121, and are mounted at the
peripheries in rigid perforated sidewall 122, which constrains
outward bowing of the fibers in bundle 115. Impeller shaft 124 is
coupled to inner cage 125 that is in turn coupled to potting
regions 116 and 117 and lower hub 126. Tubes 127 conduct gas from
an annulus within shaft 128, and include tear-drop shaped elements
129 that swing freely over tubes 127. Elements 129 automatically
adjust position responsive to changes in rotational speed of fiber
bundle 115 and blood flow, thereby reducing trauma caused to blood
contacting tubes 127. Operation of annular fiber bundle 115 is
similar to that described hereinabove for the device of FIGS. 2A
and 2B.
In accordance with the present invention, the heat exchanger of
apparatus 110 comprises coiled tube 130 disposed within housing
113. Coiled tubing 130 preferably is fabricated from a highly
conductive material, such as copper or a steel alloy. Coiled tubing
130 is spaced apart from annular fiber bundle 115 so that a gap
exists between sidewall 122 and the interior surface of the coil
when the fiber bundle is rotated. Preferably, there is also a gap
between the exterior surface of the coiled tube and the inner
surface of housing 113 to prevent the development of stagnation
zones. Adjacent turns of coiled tube 130 include small gaps 200, so
that blood exiting the fiber bundle contact and pass through the
turns of the coiled tube.
In operation, as impeller shaft 124 rotates, deoxygenated blood is
forced through fiber bundle 115 by centrifugal force. The blood is
oxygenated in the fiber bundle and then flows around coiled tubing
130 before exiting through blood outlet 15 and being returned to
the patient. Efficient thermal energy transfer occurs between the
heat transfer fluid in coiled tubing 130 and the oxygenated blood
exiting fiber bundle 115. By varying the inlet temperature and flow
rate of coolant introduced at fluid inlet 81, blood oxygenated and
pumped by integrated apparatus 110 may be regulated.
The integrated device of the present invention illustratively has
been described as employing a magnetic coupling, as shown in FIGS.
1 and 4. The present invention, however, may be readily adapted for
use with other drive systems. For example, the magnet tray may be
replaced with a direct motor drive, or may be coupled by a cable to
a drive system and control console located outside the sterile
field. Such a direct drive system could be miniaturized to be
accommodated within the sterile field. Furthermore, the controls
could be operated remotely using infrared or other such remote
controlling means. The integrated blood pump, oxygenator and heat
exchanger of the present invention also may be incorporated into a
standard cardiopulmonary bypass system that has other standard
components such as a heat exchanger, venous reservoir, arterial
filter, surgical field suction, cardiac vent, etc.
While preferred illustrative embodiments of the invention are
described above, it will be apparent to one skilled in the art that
various changes and modifications may be made therein without
departing from the invention and it is intended in the appended
claims to cover all such changes and modifications which fall
within the true spirit and scope of the invention.
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